Ferromagnetic liquids commonly are referred to as ferrofluids and typically comprise a colloidal dispersion of finely-divided magnetic particles, such as iron, Fe.sub.2 O.sub.3 (hematite), magnetite and combinations thereof, of subdomain size, such as, for example, 10 to 800 Angstroms, and more particularly 50 to 500 Angstroms, dispersed in a liquid through the use of a surfactant-type material. Typically, ferrofluids are remarkedly unaffected by the presence of applied magnetic fields or by other force fields, and the magnetic particles remain uniformly dispersed throughout the liquid carrier. Ferrofluid compositions are widely known, and typical ferrofluid compositions are described, for example, in U.S. Pat. No. 3,700,595, issued Oct. 24, 1972, and U.S. Pat. No. 3,764,540, issued Oct. 9, 1973, while a particular process for preparing such ferrofluid compositions is described more particularly in U.S. Pat. No. 3,917,538, issued Nov. 4, 1975, which describes a grinding or ball-mill technique for preparing ferrofluid compositions, and U.S. Pat. No. 4,019,994, issued Apr. 26, 1977, describing more particularly a precipitation technique for preparing ferrofluid compositions.
Ferrofluids have been suggested to be prepared using a wide variety of liquid carriers. However, current state-of-the-art ferrofluids typically employ a hydrocarbon carrier or, for example, a diester liquid, such as di(2-ethylhexyl)azelate. Liquid ferrofluids typically comprise a dispersion of colloidal magnetite stabilized by a fatty-aliphatic-acid surfactant in a hydrocarbon-liquid carrier, such as, for example, the use of an oleic-acid-type surfactant. The diester ferrofluids have found use in audio-voice-coil-damping and inertia-damping apparatus and for use in bearings and exclusion and vacuum seals. Such prior-art ferrofluid compositions often have undesirable high viscosities for the amount of magnetization required for some applications, and so it is desirable to provide stable ferrofluid compositions of a liquid polar carrier having low viscosities at higher solids content and gauss levels.